I have a 2009 24 iMac, and a 2010 27 iMac. Ethernet goes to the 27 which connects me to the world. I use the AirPort feature to communicate between the two computers. Airport enables internet use on the 24, and enables file sharing. The two computers are only 5 feet apart. Pretty much every day, the computers get amnesia, and forget their or lose their network connection. Right this second, I can file share (the little monitor icon on the upper bar tells me so), but I cannot get internet on the 24. If I could get the arrow pointing up icon to come up, I would have internet sharing. The file sharing is working, but not internet connection. This is a recurring problem. 4 calls to Apple care have provided only momentary fixes. Their last suggestion was to get AirPort Extreme. However, I think what I have should be able to be made to work. Any help out their?